A 'telnet' to port 5555 will always fail until a client is actually installed, either through a 'push' installation, or locally. Setting a TCP/IP port to 5555 is part of the component install package. This is why I didn't ask you to do this to port 5555
"Can I reinstall the Installaiton server role without crashing everything else on the CM ?"
Yes, a reinstallation server should not affect the rest of your cell. However, I understand that some folks like that extra level of safety, so, when nothing is running, stop Data Protector, and make a copy of
Program Files -> Omniback -> Config -> Server Configuration Files Windows 2003
Program Files -> Omniback -> db40 Internal Database
or
Program Data -> Omniback -> Config -> Server Configuration Files Windows 2008
Program Data -> Omniback -> db40 Internal Database
and restart DP. That way, if something goes terribly wrong, it is easy to recover
Debugging should be handled by a Data Protector support case. However, one other question did occur to me. Are you using Encrypted Control Communications? You should be able to right-click on the name fo teh cell manager, get Properties, and go to the Connection tab to see if that box is checked